1. Field of the Invention
This invention relates to a mechanism for controlling the actuation of a slide out room used on mobile living quarters (such as a recreational vehicle).
2. Discussion of the Prior Art
The width of mobile living quarters, such as recreational vehicles, is limited to that which may be accommodated for travel on the public highways. Accordingly, when the mobile living quarters is parked for use, it is desirable to be able to expand the living quarters, to increase the available living area. So-called slide out rooms have become popular to effect expansion of the available living area of such mobile living quarters. These slide out rooms are retracted into the main living area when the mobile living quarters are transported on the public highways, and then are extended from the main living quarters to provide additional living space when the mobile living quarters is parked for use. Slide out rooms are typically mounted on telescoping tubes which are mounted on the frame supporting the main living area and are actuated by hydraulic rams, electric motors, or similar actuation devices. Typically, two or more such actuation devices are required. Slide out rooms are only semi-rigid. Furthermore, the two or more actuators are often not symmetrically located with respect to the slide out room, because placement of the actuators must accommodate wheel wells and other structural components of the mobile living quarters. It is necessary to synchronize operation of the actuators, and it is desirable to be able to control the xe2x80x9croom-outxe2x80x9d and xe2x80x9croom-inxe2x80x9d positions for the actuators to assure that the room is fully extended across its entire length when the room is extended for use, and to assure that it is fully retracted across its entire length when the room is retracted to permit the mobile living quarters to be moved. Failure to fully extend or fully retract the slide out room across its entire length permits gaps to occur between the seals that seal the slide out room to the main living quarters, thus permitting moisture to leak into the unit. Failure to synchronize properly the motion of the actuators may cause undesirable deflection across the length of the room, again resulting in damage, seal problems, and unsightly appearance of the room.
According to the present invention, a pair of electric motor actuators drive an acme-threaded jack screw, or a rack-and-pinion drive, etc., connected to the slide out room to effect extension and retraction of the slide out room relative to the main living quarters. Although the invention is described in connection with a pair of electric motor actuators, it is apparent to those skilled in the art that the invention is equally applicable to systems having three or more electric motor actuators. Larger slide out rooms may require more than two electric motor actuators to effect extension and retraction of the slide out room. According to the invention, a position sensor, which may be a resistive strip secured to the actuators, or a rotary potentiometer turned by momentum of the actuators, provides a signal representative of the absolute position of the room. Optionally, a pulse generating encoder generates pulses in response to the operation of the actuators to provide an indication of movement of the actuators relative to one another. The pulses are counted to indicate the relative position of each actuator. Stop limits may be established as hereinafter provided to control the xe2x80x9cINxe2x80x9d and xe2x80x9cOUTxe2x80x9d positions of the slide out room.
According to another feature of the invention, operation of the actuators is synchronized so that the back wall of the slide out room remains substantially parallel to the wall of the mobile living quarters for most of the outward and inward travel of the slide out room. Optionally, when the slide out room reaches a point within, for example, 5% of the inner and outer stop limits, synchronization is removed, and each of the actuators travels independently of the other to the OUT or IN stop limits. Each OUT stop limit and each IN stop limit is set independently to assure that full contact with the necessary seals is made when the room is extended into its fully extended position or retracted into the fully retracted position. An optional initialization procedure is provided to permit the stops to be set individually, so that the stops may be set for each unit, since the deflection of the slide out room and positioning of the seals will vary slightly from unit to unit. According to another feature of the invention, the offset between the actuators, which is maintained by synchronization during extension and retraction of the slide out room, is set independently of the stops, thereby enabling the stops to be set to effect proper sealing.